Giving- motion to valves of steam-engines



UNITED STATES PATENT OFFICE.

HORATIO O. PERRY, OF BUFFALO, NEV YORK.

GIVING MOTION TO VALVES 0F STEAM-ENGINES.

Specification of Letters Patent No. 181,925, dated December 22, 1857,

To all whom it may concern:

Be it known that I, HoRATIo O. PERRY, of Buffalo, in the county of Erieand State of New York, have invented a certain Improvement in GivingMotion to Valves of Steam-Engines; and I do hereby declare that thefollowing is a full, clear, and exact description `of the same,reference being had to the accompanying drawings and to the lettersmarked thereon.

Figure l is a side view, Fig. 2 an end elevation, and Fig. 3 a plan ofan oscillating engine, with my improvements.

Similar letters of reference indicate like parts in both drawings.

Ever since the action of steam has been closely investigated, andexperiments on the economy of engines have been rigorously conducted, ithas been well understood that there is economy in closing the steamvalves before the termination of the stroke of the pist-on to allow vthesteam to act eXpansively; also that there is economy in varying thepoint of cut off, as it is termed, at will, so as to avoid the necessityfor throttling the steam to control the motion of the engine; also thatthere is economy under such circumstances in shut-ting the steam valvesvery rapidly, so as to avoid wiredrawing the fluid ,-and ever since theproperties of matter have been investigated it has been will establishedthat shocks and concussions are objectionable in all kinds of mechanism.It has however been diiiicult to construct steam engines in such manneras to fulfil all the first named conditions without involvingdificulties in regard to the last named point.

My improvement applies to such engines and such only as employsemi-rotating or rolling valves which are released and allowed to shutautomatically. It relates to the means of shutting such valves when theyare detached from the positive mechanism, and of stopping the motionwith-out shock at the right point. It-s effect is to shut such valvesrapidly and quietly without necessitating any dash-pots or air cushionsto stop the motion.

It consists first in acting `on the valve by a force independent of theengine in the manner fully represented and described blow, so that whilethe force has great effect in turning the valve when the latter is firstreleased and consequently moves it very rapidly at that instant, itseffect decreases to nothing as the valve assumes the position at whichit is desirable that it shall stop, and becomes a negative and retardingforce when it chances to revolve by momentum past that position. Iaccomplish this by subjecting to a tensile strain a link so connectedthat it shall be in a line radial to the axis (or at its dead point)when the valve is in the position to stop.

It also consists, in connection with the first, in the employment in themanner fully represented and described below, of a piston acted on bythe steam to give the necessary tensile strain to the link, in orderthat said tensile strain may be proportional to the resistance. Theresistance to the motion of the valve is due'mainly to the pressure ofthe steam, and it increases or diminishes as said pressure increases ordiminishes, and it is consequently important not only to make the forcegreatest at the commencement of the motion and nothing at thetermination thereof, but also, to make the whole sum of the force or theunits of work expended in the operation vary with the pressure of thesteam, so that the motion will be destroyed at or near the same pointwhether the pressure be greater or less.

My invention therefore in its simplest form consists in simply shuttingthe valve by a force peculiarly applied; in its more approved form theforce is also made to vary with the necessities of the case, and in itsmost perfected form it is also applied in such a direction that thevalve is partially balanced thereby. The automatic closing of the valvesbeing performed by the balance pistons, the force impelling them isalways proportional to the pressure of the steam; and therefore justsufficient for the purpose, without necessitating any considerablesurplus power and consequently without producing any considerable amountof momentum to be annihilated after the movement is completed.

To enable others skilled in the art to make and use my invention, I willproceed to describe its construction and operation. I apply it alike todirect acting or beam engines, or to oscillating engines, which latterVis the style represented in the drawings. It is only necessary, whenthe engine is not an oscillating engine, to give the eccentrica greaterthrow so that the proper motion will always be imparted to the valve.

A represents one `of the forms of valve to which my invention isapplicable. It is mounted loosely on the shaft B, and lits nicely in thehollow cylindrical surface C. To the point D, on this valve, is attachedby means of the linkE, a small piston F, fitting nicely in acorresponding cylinder, as represented. This pressure of the steam inthe steam chest tends to urge this piston up, and thus by the tension onthe link E constantly impels the valve to assume and maintain theposition indicated by the dark lines in the drawings. It also relievesthe valve A from a part of the force which would otherwise press it withgreat Aviolence against C.

G is a short port leading, as directly as possible to the end of thecylinder.

H is a port leading from the vicinity of G to allow the escape of theexhaust steam. The valve A has a hollow throat A through which, when thevalve is in a suitable position, the steam from Gr may freely escapeinto H. Small springs, not represented, are introduced between the shaftB, and the valve A which serve to keep the valve A in steam-tightContact with C when there exists no pressure of steam in the steamchest. rlhe shafts B project through stuffing boxes in t-he side of thesteam chest, and carry on their extremities parts which alternately moveand release the valve by the aid of said valve-stems, so that thevalveis opened at the proper time by a positive mechanism through the aid ofsuch parts, and is released at the period when it is desired for thevalve to shut. Whenever the valve is thus released it is immediatelyrevolved into the position represented, by the pull on the link E and bychanging' the releasing devices or the positions of some parts thereofthe valve may be released at any desired point less than a half stroke,so that my device is a variable cut-oft', possessing very obviousadvantages, and closing the valves independently of the openingmechanism, and also independently of any weights or springs.

The resistance to the closing of a valve arises mainly from the pressureof the steam thereon; and as this is necessarily variable in allengines, it is diiiicult to provide just suiicient force for the purposeby other devices; but mine allows a very perfect equalizing of the powerand the resistance. rIlhe tpiston F must be made of such size as nearlyto equal in area the whole effective area of the valve A and thus torelieve it of most of its load, and must be connected, as represented,to a convenient point on the opposite side of the shaft, so that itspull will always tend to close the Valve when released, and theconnecting link must be attached to the valve at such a Vdistance fromthe center of the shaft that it can act to advantage in so doing. Solong as the pressure of the steam is constant the pull on the link E isso, but this disposition of the parts makes the leverage of F, or, inother words, the effect of this force in giving motion to A diminish asthe valve approaches its proper position, and be reduced to nothing whenit is fully attained. As a consequence, no dash-pot or air-cushion isrequired by my invention, but the valve is always stopped by friction aton near its most desirable position. The face of the valve A whichserves to cover the port Gr is purposely made considerably wider thanthe port Gr, so that if excessive friction exists in consequence of drysteam or tight packing, the valve may move automatically to a lessdistance than ordinary; or if unusual lubrication be afforded it maymove farther than ordinary, and no bad effects will ensue in eithercase. It will be noted that the pull on the link E becomes opposed tothe motion of the valve so soon as the latter has revolved beyond itsmost desirable position.

An opening of some kind must be left in the cover of the cylinder F or apipe F must be provided to communicate from thence to the exhaustpassages at some convenient point so as to allow the escape of whateversteam may chance to leak past the balance piston F and thus to insurethe existence of only the same amount of pressure per square inch asobtains within the cavity A.

I do not confine myself to the precise form of valve represented in theaccompanying drawings. I do not require that the positive mechanismshall move the valve in both directions from its most desirable shutposition as my invention is equally applicable, and production ofequally good results when applied to a valve without a hollow throat andwhich simply covers a single port and uncovers the same by turning to alimited extent in one direction only; but I do conine the use of myinvention to its connection with rotating or' partially rotating valveswhich are opened by a positive mechanism and then detached at or beforethe completion of the stroke and allowed to shut automatically.

What I claim as my invention and desire to secure by Letters Patent isas follows:

1. I claim the above described method of shutting a rolling or partiallyrotating valve by pulling on a link so attached that its effect inrotating the valve decreases as the valve assumes its most desirableshut position and tends to revolve it in the reverse direction when thevalve revolves by momentuin past such position When operated resistance,for the purpose of enabling the substantially as and for the purposeherein valve to stop in the proper position under all 10 set forth. h bd b d h d pressures of steam as above set forth.

2. Ialso claimt ea ove esori e Inet o of operating said link by thepressure of the HORATIO O PERRY steam so that the Whole amount of powerWitnesses: available in shutting shall be always pro- JOHN D. SHEPARD,portional or very nearly proportional to the WILLIAM HENRY EASTMAN.

